Polypronuclear embryos after in vitro fertilization.

Triploidy occurs in 1% to 3% of recognized conceptions in vivo. In vitro fertilization (IVF), which places large numbers of sperm in proximity to the oocyte, may increase the risk of triploidy. The risk also could be influenced by stimulation protocols that differentially affect egg quality. We found no significant difference in triploidy when cycles were stimulated with clomiphene citrate/human menopausal gonadotropin (3.2%) compared with gonadotropin-releasing hormone analog/human menopausal gonadotropin stimulation (4.4%). Triploidy was less common with male factor infertility (0.7%) compared with other causes of infertility (3.4% to 3.8%). Triploid embryos can develop to cleavage stages indistinguishable from those generated by diploid embryos. Thus, identifying and discarding embryos with greater than 2 pronuclei is a vital function of an IVF laboratory.